Certain medical treatments include dispensing of a medication to a patient over an extended interval of time, known as infusion therapy. For example, insulin, HIV drugs, pain medication, nutrients, antibiotics, and anti-cancer treatments are just a few examples of medications which are sometimes used in infusion therapy. In general, infusion therapy includes the moving of an appropriate amount of medication from a fluid reservoir into the patient in a controlled manner.
A number of different pumps suitable for use in infusion therapy are known. For ambulatory patients, a portable infusion pump results in less disruption to the patient's lifestyle and is therefore often preferred. Portable infusion pumps present several design challenges.
One important aspect of infusion therapy is ensuring that the proper amount of medication is delivered to the patient. It is sometimes necessary to be able to adjust the flow rate provided by the infusion pump, since the flow rate required may depend on the medication and the patient. It is also desirable that the cost of a portable infusion pump is kept low.
Programmable infusion pumps are known, which allow the setting of parameters such as flow rate and the like to be set by way of various controls. Controls (e.g., knobs, buttons, etc.) and indicators (e.g., lights, displays, etc.) provided to enable such programming adds undesirable cost to the infusion pump. Additionally, some controls can be difficult or cumbersome to operate.
Many drugs are infused at only a few defined rates and in a few defined volumes. Hence, one known solution is to provide a family of portable infusion pumps, each of which only operates at a single rate/volume setting. Although the individual devices are easy to use and relatively inexpensive, it is necessary to stock several different units to accommodate different prescriptions, which can be inconvenient.
Fixed settings do not work well with some therapies, such as so-called patient controlled analgesia (PCA). In PCA, typically three pump parameter settings are programmed: base flow rate, bolus amount and bolus lockout time. The base flow rate is a regularly delivered amount of medication. The bolus amount is an addition to the base flow rate which is delivered on demand of the patient. A lockout interval limits how frequently the bolus amount is actually administered.
In PCA it is desirable that programming of the pump can only be performed by the physician or assistant, otherwise a patient access can defeat the lockout interval. Known techniques for limiting access include physical covers which mechanically lock in place to prevent access to the controls, and electronic programming systems which require the pump to be placed on a special programming base for settings to be changed. Both approaches are cumbersome and add cost to the pump.